Dam fix too costly, Avista says

Soaring costs for steel and concrete have pushed the price tag of retooling an Avista Utilities dam near Sandpoint too high, according to company officials.

The Spokane utility is trying to find a fix to a vexing fish problem: its large Cabinet Gorge Dam on the Clark Fork River on the border of Idaho and Montana is blamed for making river conditions deadly for endangered bull trout and other fish.

Put simply, the dam can’t handle all the water from snowmelt and spring rains that swell the Clark Fork on its course to Lake Pend Oreille. When the excess water spills over the tall concrete dam and plunges into a deep pool, the force injects high levels of nitrogen and oxygen into the water.

The process creates river water that is too high in what scientists call “total dissolved gas,” and basically gives fish a deadly case of the bends. Fish swimming deep in the river or in Lake Pend Oreille absorb this dissolved gas in the bloodstream. When they swim toward the surface, the gas forms bubbles in fine tissues such as the eyes, skin and gills, blocking the flow of blood.

Avista, as recently as this summer, thought it might be able to solve the problem by refurbishing two old tunnels that were originally dug to divert the river when the dam was built in the 1950s. The extra water that the dam couldn’t handle would be sucked through the tunnels and let into the river rather than spilling over the dam.

The cost of completing the first tunnel was predicted to be $38 million. But further pricing analyses pushed the figure to $58 million, according to the company’s most recent financial filings. On top of that, said Avista hydropower projects manager Steve Fry, the tunnels solution may not be as promising as hoped.

The company said the river water wouldn’t be substantially improved and made more habitable for the rare trout, or other species suffering the affliction called fish-bubble disease.

Avista continues to talk with government agencies in charge of water quality and fish about what can be done within the next few years to make changes to a river that has been historically tough on fish.

Avista knows it will have to spend money, said spokesman Hugh Imhof. Cabinet Gorge is a valuable asset, capable of generating enough electricity to serve 170,000 homes in North Idaho and Spokane.

The company wants to explore whether it can spend money on other projects that might better lead to the ultimate goal of more and healthier fish in the lower Clark Fork River and in Lake Pend Oreille, he said.

Avista’s other conservation efforts to offset the effects of its two dams on the river earn high praise from regulators and local communities.

The company’s license to operate the dams requires it to meet fish and water quality regulations.